Method for decomposing polyesters containing aromatic moieties, a denier reduction method of fiber, and microorganisms having activity of decomposing the polyester

ABSTRACT

A polyester containing aromatic moieties is contacted with microorganisms having the activity of decomposing the polyester to decompose or reduce it. Preferably, either or both of  Trichosporon  FERM BP-6445 or  Arthrobacter  FERM BP-6444 was contacted with the polyester to decompose or reduce it. A fiber made of the polyester or a cloth made of such fiber may be reduced by contacting it with the microorganisms having the activity of decomposing the polyester.

BACKGROUND OF THE INVENTION

1. Field of the invention

The present invention relates to a method for decomposing polyesterscontaining aromatic moieties, a method for reducing a fiber made of suchpolyesters, and microorganisms capable of decomposing fibers made ofsuch polyesters.

2. Description of the Related Art

A law for recycling a container and wrapping was enforced in April, 1997for reducing such wastes and the resulting environmental pollution,which has been attracting public attention. A grace period of 3 years isprovided for a container and wrapping made of a plastic material, whichwill be under the law, necessitating a high cost for the recycling, fromApril, 2000. Polyethylene terephthalate, universally used for acontainer of soft drink and seasoning, also will be under the law.Manufacturers try to collect and recycle such container.

However, polyesters containing aromatic moieties, such as polyethyleneterephtalate or polybutylene terephthalate, are finally treated byreclamation or burning-up. The burning-up process inevitably producesharmful wastes and the reclamation may produce-floating wastes on water,both leading to further environmental pollution.

Therefore, a container or wrapping material made of a polymer containingaromatic moieties, and clothes and-ornaments made of the polyesterdischarged in an apparel industry will require high costs for theirrecycling and should finally be treated by reclamation or burning-up. Asolution for treating such materials has been demanded.

SUMMARY OF THE INVENTION

An object of the invention is to provide a method for treating amaterial or fiber made of a polyester containing aromatic moieties, withadverse effects on environment substantially reduced.

Another object of the invention is to apply such treating method todenier-reduction process of fiber.

The present invention provides a method for decomposing polyesterscontaining aromatic moieties, the method comprising:

contacting a microorganism having an activity of decomposing polyesterscontaining aromatic moieties with the polyester to decompose it.

The inventors succeeded in decomposing a polyester containing aromaticmoieties by means of microorganisms for the first time in the globe.Although aliphatic polyesters have been known to be biodegradable, ithas never been known that the polyesters containing aromatic moietiesare susceptible to decomposition by microorganisms. As a result, theinvention may decompose and degrade such aromatic polyesters withoutenvironmental pollution, then decomposition products with low molecularweights may be returned into a substance-recycling system in naturalenvironment.

The inventive method for decomposing polyesters containing aromaticmoieties may be applied to a container, a wrapping material, as well asa fiber and cloth, each made of such polyesters. When the wastescontaining the polyesters are subjected to composts, microorganismsincluded in the composts rapidly decompose the polyesters into nontoxicsubstances. Alternatively, when the wastes containing the polyesters arereclaimed, microorganisms may be included in wastes to decompose thepolyesters. Such polyester wastes, contained in the composts or thereclaimed wastes, may be partly or wholly decomposed.

An effective treatment has not been found yet to treat so called apet-bottle (a bottle made of polyethylene terephthalate). The inventionprovides a method for treating such bottle without leaving furtherwastes in natural environment.

The other treating methods, such as reclamation and burning-up, mayproduce harmful substances. The inventive microorganisms capable ofdecomposing the polyesters may survive for a long time, even whenutilizing the polyesters as a sole carbon source, thereby probablyalleviating the possibility of producing harmful substances.

The inventors also succeeded in applying the inventive decompositionmethod for denier reduction process of the surface of fibers made ofpolyesters containing aromatic moieties. The inventive reducing methodproduces no decomposition residue, which has been inevitably produced inthe previous caustic (denier) reduction method of a fiber, therebyproviding technique suitable for environment. The inventive reductionmethod is also useful for obtaining a fiber with better fitting andappearance. For example, a cotton fiber has been treated to improve itsfitting and appearance by means of cellulase derived frommicroorganisms. The inventive denier reduction method may also produce afiber and cloth made of the polyesters with improved fitting andappearance. Moreover, the thus obtained fiber has small depressions,hollows and ditches or grooves on the surface formed during thereduction process, thus facilitating its dyeing.

The inventors have confirmed the activity of decomposing a polyestercontaining aromatic moieties, in the following microorganisms.

-   (1) Trichosporon FERM BP-6445-   (2) Arthrobacter FERM BP-6444

A polyester containing an aromatic moiety is a polyester produced bypolymerizing monomers, at least one of the monomers being an aromaticcompound. Such polyester is not particularly limited. However, suchpolyester may preferably be a polyalkylene phthalate, isophthalate orterephthalate, more preferably be polyethylene terephthalate,polypropylene terephtlhalate, or polybutylene terephthalate, and mostpreferably be polyethylene terephthalate or polybutylene terephthalate.The polyester may be a homopolymer of an aromatic compound, or acopolymer of aromatic compounds, or a copolymer of an aromatic compoundand an aliphatic compound. The aromatic compound is not limited, andpreferably be alkylene terephthalate such as ethylene terephthalate,propylene terephthalate and butylene terephthalate.

These and other objects, features and advantages of the invention willbe appreciated upon reading the following description of the inventionwhen taken in conjunction with the attached drawings, with theunderstanding that some modifications, variations and changes of thesame could be made by the skilled person in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference is made to theattached drawings, wherein:

FIG. 1 is a photograph showing the surface of a fiber made ofpolyethylene terephthalate, taken by an electron microscope (at amagnitude of 3000), after treating it with a yeast-like microorganismhaving the activity of decomposing a polyester containing aromaticmoiety for 30 days,

FIG. 2 is another photograph showing the surface of a fiber made ofpolyethylene terephthalate, taken by an electron microscope (at amagnitude of 3000), after treating it with the same yeast-likemicroorganism as FIG. 1 for 30 days,

FIG. 3 is a photograph showing the surface of a fiber made ofpolyethylene terephthalate, taken by an electron microscope (at amagnitude of 3000), after treating it with a bacterium having theactivity of decomposing a polyester containing aromatic moiety for 55days,

FIG. 4 is another photograph showing the surface of a fiber made ofpolyethylene terephthalate, taken by an electron microscope (at amagnitude of 3000), after treating it with the same bacterium as FIG. 3for 55 days,

FIG. 5 is a photograph showing the yeast-like microorganism, taken by anoptical microscope at a magnitude of 1500,

FIG. 6 is a photograph showing hyphae and oidia (at a magnitude of 470)formed after cultivating the yeast-like microorganism of FIG. 5 on acorn meal agar plate at 25° C. for 3 days,

FIG. 7 is a photograph showing the bacterium having the activity ofdecomposing a polyester containing an aromatic moiety, taken by anoptical microscope at a magnitude of 1500,

FIG. 8 is a photograph showing the bacterium of FIG. 7 after cultivatingit for 8 hours, and

FIG. 9 is a photograph showing the bacterium of FIG. 7 after cultivatingit for 72 hours.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(Screening of Microorganisms Capable of Decomposing a PolyesterContaining an Aromatic Moiety)

The inventors found a method of cultivation for screening amicro-organism capable of decomposing a polyester containing aromaticmoieties, such as polyethylene terephthalate. Polyethylene terephthalateis insoluble in water and usually has a crystalline structure. Theinventor therefore added fibers, made of an amorphous or non-crystallinepolyethylene terephthalate, in a medium having the-followingcomposition. Fibers were used for facilitating the judgement on whetherthe decomposition took place or not, in other words, the screening of amicroorganism capable of decomposing the polyester. Moreover, a mediumcontaining polyesters having aromatic moieties as a sole carbon sourcewas used for enrichment culture. Used Medium yeast extract   0.1%ammonium sulfate   0.2% salt mixture FeSO₄.7H₂O  0.001% CuSO₄.5H₂O0.0001% ZnSO₄.7H₂O 0.0001% MgSO₄.7H₂O 0.0001%

The used medium had unadjusted pH. 7 ml of the medium was contained ineach tube, which was put into an autoclave and then sterilized at 120°C. for 15 minutes. Thereafter fibers made of amorphous polyethyleneterephthalate were added into each tube so that its content is made 0.2percent. Each fiber has a diameter of 120 micrometer, a length of 5centimeter, 12 fibers were added into each tube.

400 soil samples collected from many places in Japan were screened. Aspoonful (spertel) of each soil sample was added into each medium and itwas cultured at 25 to 30° C. for 1 week to select soil sample with thegrowing of a microorganism confirmed (first stage screening). Each soilsample was then subjected to subculture with its medium replaced everytwo weeks to perform enrichment culture for two months. At the end ofsecond month, fibers made of polyethylene terephthalate were drawn fromeach culture medium to measure their tensile strengths usingTensilon/JTM-4L (Toyo Measuring Instruments Co. Ltd. 50 mm /min). Whenthe tensile strength of the treated fiber is considerably reducedcompared with that of an untreated fiber (blank), such fiber is furtherobserved by means of a scanning electron microscope (Hitachi S-800).These results of the tensile strength and surface observation wereconsidered to judge whether it is decomposition-positive or negative(second stage screening).

(Isolation of Microorganisms and its Activity of Decomposing a PolyesterContaining Aromatic Moieties)

Two samples were selected from several soil samples in which the tensilestrengths of the fibers were reduced. A microorganism was isolated fromeach of the selected two samples as a single colony. Each micro-organismhas the activity of decomposing a polyester containing aromaticmoieties. A yeast-like microorganism was isolated from one sample and abacterium was isolated from another. The ratio of the tensile strengthof the treated fiber to that of the untreated fiber (blank) was reducedto 60 percent after 30 days, in the sample from which the yeast-likemicroorganism was isolated. The ratio of the tensile strength of thetreated fiber to that of the untreated fiber (blank) was reduced to 92percent after 30 days and 51 percent after 55 days, in the sample fromwhich the bacterium was isolated.

FIGS. 1 and 2 show photographs of the surface of the fiber treated withthe yeast-like microorganism, taken by an scanning electron microscope(at a magnitude of 3000). As shown in the FIGS. 1 and 2, manycircular-shaped craters or depressions were observed on the surface ofthe fiber.

FIGS. 3 and 4 show photographs of the surface of the fiber treated withthe bacterium by a scanning electron microscope (at a magnitude of3000).

As shown in the FIGS. 3 and 4, many eroded regions were formed and eacheroded region tends to elongate in the longitudinal direction of thefiber to form small ditch or groove. Therefore, the yeast-likemicroorganism and bacterium may decompose the fiber to form erodedregions with characteristic patterns and morphology different form eachother. Therefore, the fiber may be more effectively decomposed orreduced by contacting both of the yeast-like microorganism and bacteriumtogether with the fiber.

(Identification of the Yeast-like Microorganism)

This microorganism belongs to Trichosporon. Its international depositnumber is Trichosporon FERM BP-6445. Trichosporon is an incomplete yeastbelonging to basidiomycetes which forms hyphae and oidia. The known mainsources of Trichosporon are foods, intestines including that of a human,water, waste water, trees, saps or the like (reference: Kreger-van Rij,N. J. W. ┌The Yeasts, 1984, Elsevier Science Publishers B. V. Barnett,J. A., Payne, R. W. and Yarrow. D. ┌Yeasts: Characteristics andidentification┘ Second edition, Cambridge University Press) Morphologyof vegetative cell spherical, ellipsoidal, cylindrical Form ofmultiplication multipolar budding, forming oidia Liquid cultureprecipitation and coating were observed (25° C., 3 days) Pseudomyceliaobserved (25° C., 3 days) Hyphae observed (corn meal agar plate culture,25° C., 3 days) Oidia observed (corn meal agar plate culture, 25° C., 3days) Ascospores not observed on Adams, Gorodkowa, malt, YM, V-8 andpotato dextrose media) Fermentation of glucose negative Assimilation ofinositol positive Assimilation of nitrate negative Decomposition of ureanegative (not typical form) Coloration of DBB positive Xylose in cellwall positive

FIG. 5 shows a photograph of the yeast-like microorganism, taken by anoptical microscope (at a magnitude of 1500). FIG. 6 is a photographshowing its hyphae and oidia observed after cultivating themicroorganism on a corn meal agar plate medium at 25° C. for 3 days,taken by an optical microscope (at a magnitude of 470).

(Identification of the Bacterium)

(Arthrobacter FERM BP-6444)

The bacterium was identified to belong to Arthrobacter, based on itsmorphology, physiological properties, celluler components, and a GCcontent: (Sneath P. H. A., Mair, N. S., Sharpe M. E. and Holt J. G.┌Bergey's Manual of Systematic Bacteriology┘ Vol. 2, 1986, Wiliams andWilkins: Holt J. G., Krieg N. R., Sneath P. H. A., Stanley, J. T. andWiliams, S. T. ┌Bergey's Manual of Determinative Bacteriology┘ ninthedition, 1994, Wiliams and Wilkins).

Arthrobacter belongs to an asporogenic gram-positive rod bacteriashowing polymorphism. Morphology polymorphic rod bacteria Gram stainpositive Spores negative Motility positive Relation to oxygen aerobicOxidase negative Catalase positive OF negative Resistance to aciditynegative Color of colony not forming characteristic pigments Rod coccuscycle positive Elongation of peripheral negative cells in colony Cellwall Diamino acid lysine Acyl-type acetyl-type Arabino-galactan polymernegative (assumed using acidic hydrolysis products of the whole cell)Main quinone series MK-9 (H2) GC content in the DNA 65 (mole percent:measured by HPLC method)

FIG. 7 is a photograph showing the bacterium, taken by an opticalmicroscope (at a magnitude of 1500). FIG. 8 shows the bacterium aftercultivating it in EYGA medium at 30° C. for 8 hours, and FIG. 9 after 72hours.

(Denier-reduction Treatment of a Cloth Made of Polyester-fibersContaining Aromatic Moieties)

Cloths made of polyethylene terephthalate were reduced by contactingthem with the yeast-like microorganism or bacterium, using the abovedescribed medium samples used for screening.

In experiment A, a cloth made of crystalline polyethylene terephthalatefibers, with a dimension of 18 mm×18 mm and a weight of 2.083 gram, wasdipped in the above medium, to which the yeast-like microorganism wasinoculated. Then, it was cultured for 55 days at 30° C., with its mediumreplaced every 2 weeks. After the cultivation, the cloth was taken outfrom the liquid culture and weighed. Experiments B and C were alsoperformed, except that the bacterium was added instead of the yeast-likemicroorganism in the experiment B and both were added in the experimentC.

As a result, the weight of the cloth was reduced to 1.753 gram in theexperiment A, reducing 15.8 percent of its original weight. The weightof the cloth was reduced to 1.751 gram in the experiment B, reducing15.9 percent of its original weight. The weight of the cloth was reducedto 1.729 gram in the experiment C, reducing 17.0 percent of its originalweight. Moreover, fitting and appearance were improved when observed byeyes, and the handling was considerably changed.

1-13. (canceled)
 14. A reduced fiber produced by a denier reductionmethod comprising contacting a microorganism having activity fordecomposing a polyester containing an aromatic moiety, with the fiber toreduce the denier of the fiber.
 15. A reduced fiber produced by a denierreduction method as claimed in claim 14 wherein the fiber is reduced bycontacting it with Trichosporon FERM BP-6445.
 16. A reduced fiberproduced by the denier reduction method as claimed in claim 14 whereinthe fiber is reduced by contacting it with Arthrobacter FERM BP-6444.17. A reduced cloth produced by the denier reduction method as claimedin claim 14 wherein a cloth made of the fiber is contacted with themicroorganism to reduce the weight of the cloth. 18-23. (canceled)